Department of Diagnostic Imaging, The Hospital for Sick Children , Toronto, ON , Canada ; Neuroscience and Mental Health Program, The Hospital for Sick Children Research Institute , Toronto, ON , Canada ; Department of Medical Imaging, University of Toronto , Toronto, ON , Canada.

(A) Interface of PTSD and mTBI symptomatology, and empirical evidence of altered spontaneous functional connectivity patterns in a resting-state paradigm. Both patient groups show elevated connectivity compared to their respective control groups, with increased coupling in PTSD mediated by high-frequency (high gamma-range, 80–150 Hz) oscillatory synchronization; in the mTBI group connectivity is enhanced in the low-frequency range (delta–theta range, 1–3 and 3–7 Hz), and is typified by envelope amplitude cross-correlations/temporal covariations. (B) Hypothesized role of coupled oscillators in interregional brain communication, and the distinct mechanisms of “intrinsic coupling modes.” These are divided into phase ICMs (facilitating communication between regions 1 and 2, described in I), and envelope ICMs (regulating temporally coordinated activity between regions 2 and 3, described in II). In contrast to these mechanisms, regions 1 and 3 are neither phase synchronized nor amplitude coupled, and therefore communication is suppressed between these regions. (C) Summary of findings and the theorized phenomenological significance of these atypical connectivity patterns.